JPS6449663A - Head temperature control system - Google Patents

Abstract

PURPOSE:To increase a printing speed by removing nonuniformity of a printing density owing to dispersion of a head temperature, by executing control of an electrothermal time with hardware composed of an integrating circuit, a voltage control oscillating circuit, and a timer circuit. CONSTITUTION:A head driver circuit 6 heats a head by application of current when a drive signal b is logical '1'. A drive signal 6 is fed back to a transistor 1, which supplies a current an integrating circuit 3 via a thermistor 2. A voltage control oscillating circuit 4 controls frequency of a clock signal (c), and as an input voltage increases, an oscillating voltage rises. The drive signal (b) outputted from a timer circuit 5 is triggered by trigger input a to become logical '1'. When logical variation of the clock signal (c) is counted several times, it becomes logical '0'. Since time from being triggered to end of counting is short in the case where frequency of the clock signal (c) is high, time while a drive signal a becomes logical '1' becomes short. In the case where frequency of the clock signal (c) is low, a drive time becomes long. Heating time of the head for a dot to be printed is controlled thus by a past electrothermal time.